Nutrient availability correlates with bicarbonate accumulation in marine and freshwater sediments – Empirical evidence from pore water analyses

In the last decades, eutrophication has become a major cause for concern in aquatic ecosystems worldwide. Apart from external nutrient loading, release of dissolved nutrients from sediment pore water into the water layer contributes importantly to eutrophication. Theory implies that pore water HCO3- and nutrient mobility are linked, because anaerobic organic matter breakdown stimulates release of HCO3- and nutrients, while HCO3- stimulates decay rates by increasing buffer capacity and pH. An investigation was performed on how HCO3- relates to commonly measured eutrophication-related variables in freshwater and marine sediments, by analyzing a database of 71 marine and 206 freshwater samples, using linear and non-linear regression. Results demonstrate that HCO3- is indeed strongly related with NH4+ and PO43- in both freshwater and marine pore waters. Moreover, HCO3- also correlated with sulfide levels in marine sediments. Contrastingly, no relationship was found with variables describing total nutrient content (i.e. organic matter, total P and N), suggesting that these do not reveal information on nutrient availability in aquatic sediments.

Research highlights
► Bicarbonate correlates with ammonium and o-phosphate in pore waters of marine and freshwater sediments.
► Bicarbonate also correlates with sulfide levels in marine sediments.
► No relation was found with variables describing total nutrient content.